User guide

The information in this appendix describes hard drive array concepts, data
protection methods, including fault-tolerance options, and data reliability
features of the Compaq RA4000 Controller installed in the Compaq RA4000.
Before configuring the RA4000 Controller, review the following general
information so that you will be familiar with the terms and concepts required
for configuration.
A drive array is a collection of hard drives (physical drives) grouped together
to create an array of physical drives. An array is made up of one or more
subsets called logical drives (sometimes called logical volumes) that are
spread across all physical drives in the array. Operating systems view logical
drives as a single, contiguous storage space although it is made up of parts of
several physical drives.
The generic drive array illustrated in Figure E-1 consists of two logical drives
spread across three physical drives. Figure E-2 through Figure E-4 illustrate
other drive array configurations.